1. Field of the Invention
The invention relates to plunge routers, and in particular, to an improved mechanism and method of adjusting the base-plate of the router relative to the bit of the router.
2. Problems in the Art
Router mechanisms have a wide range of applications, particularly with respect to woodworking. A particular type of router is called a plunge router. For example, U.S. Pat. No. 4,770,573 to Monobe, discloses a basic configuration of such routers. A base plate is used to support the router against the surface to be routed. A bit is usually centered the in base and is rotated by a motor. Handles are used to grip the router if it is used in a freestanding mode.
As set forth in U.S. Pat. No. 4,770,573, incorporated by reference in its entirety herein, a unique aspect of plunge routers is that they utilize support members or columns in between the base and the main housing. The support columns are longitudinally slideable in receiving chambers. Springs push against the interior ends of the support columns to urge them outwardly and thus bias the base away from the housing of the router. This arrangement allows the base to be positioned in a normal position such that the bit does not extend past the plane of base. The base of the plunge router can therefore be placed on a surface to be routed and then force applied to the router housing (against the springs) to move the bit down to the work surface to start routing in the middle of a work surface. Without such an arrangement, it would be very difficult to maneuver a router to a precise starting point on the interior of a surface to be routed.
Note, however, that it is sometimes desirable to invert a plunge router and install it upside down in a table or other support so that it could be used as a table router. An example of such an arrangement is disclosed in Neilson U.S. Pat. No. 5,139,061, incorporated by reference in its entirety herein. Plunge routers have the flexibility of being used in a portable, hand-guided manner (See Monobe U.S. Pat. No. 4,770,573) or in a table-mounted orientation (Neilson U.S. Pat. No. 5,139,061).
Conventionally, plunge routers allow some adjustment of the position of the base relative to the bit. As can be seen in Monobe U.S. Pat. No. 4,770,573, and also in Walter U.S. Pat. No. 5,725,036, incorporated by reference in its entirety herein, the normal bit adjustment is a knob at the end of a threaded rod, which extends along the motor housing of the plunge router. The operator can turn the knob to move the base farther away or closer to the bit as desired. While such an arrangement is fairly satisfactory when the plunge router is used in the hand-manipulated mode, it is cumbersome to adjust when the plunge router is used in the fixed table-mode like Neilson U.S. Pat. No. 5,139,601. The operator many times has to reach underneath the table and it is sometimes difficult to locate the knob to adjust the router.
This very problem is recognized in U.S. Pat. No. 5,918,652 to inventor Tucker. The solution in Tucker is utilization of a complex assembly, including a lever arm, that still would be positioned under a router table if the plunge router were used in that manner. Tucker represents a relatively costly and complex attempted solution that is not entirely satisfactory.
The Monobe patent discloses the basic structure of a plunge router and one method of adjusting base plate to bit distance. As with most plunge routers, Monobe illustrates the problem with adjustment requiring turning of a knob attached to a threaded rod at a location on the router opposite the base plate. She operator is basically adjusting the bit relative to the base plate from a position almost as remote as possible from the location of the bit. In routing, it is many times, if not most times, important to have very precise positioning of the bit relative to the base. The Monobe-type adjustment mechanism not only makes it difficult to have precise adjustment (because it makes it difficult for the operator to both accurately view or measure bit location relative to the base while also operating the adjustment mechanism), but also the arrangement in combination with the plunge router makes it difficult to hold or position the plunge router during adjustment. For example, if the base plate is placed on top of a table, adjustment of the bit lower than the base plate is not possible. If the router is inverted with its opposite end placed on the table, the adjustment mechanism many times extends below the plane of the end of the router. One must therefore place the router near the edge of the table so that the adjustment mechanism extends lower than the table or bench top. The operator must maintain and support the router with one hand and operate the adjustment with the other while attempting to monitor bit height. This is difficult. If the router is laid on its side, many times it makes it difficult for the adjustment to be accessed or easily operated. The base is then usually lying at an oblique angle making it more difficult to measure the bit height. Again, as previously mentioned, if the router is mounted in an inverted fashion in a router table, it is cumbersome and difficult to reach under and adjust the bit height.
Neilson attempts to address this issue by placing a threaded rod through a support column which has an end accessible for connection to a rotary crank at the table surface. This modification allows adjustment of bit height from on top of the table. However, it makes it very difficult to adjust bit height when the router is used in a hand-held mode. Also it is very cumbersome and slow to crank the router housing from a fully extended position up to a position where the bit extends above the router table surface. Thus, the Neilson arrangement is basically dedicated to router table use of the router. The Walter adjustment conversion kit requires modifications of the plunge router that eliminates some of the normal plunge router functions.